Electrical power control unit having a switch and connector with safety interlock



Nov. 15, 1966 ELECTRICAL POWER CONTROL UNIT HAVING A SWITC Filed April 12, 1965 c. MACKIEWICZ 3,286,051

AND CONNECTOR WITH SAFETY INTERLOCK 2 Sheets-Sheet 1 Jill.

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ELECTRICAL POWER CONTROL UNIT HAVING A SWITCH AND CONNECTOR WITH SAFETY INTERLOCK Filed April 12, 1965 2 Sheets-Sheet 2 I NVENTOR.

HTT'ORNEYS United States Patent 01 3,286,051 Patented Nov. 15, 1966 3,286,051 ELECTRICAL POWER CONTROL UNIT HAVING A SWITCH AND CONNECTOR WITH SAFETY IN- TERLOCK Czeslaw Mackiewicz, Trumbull, Conn., assignor to Harvey Hubbell, Incorporated, Bridgeport, Conn., a corporation of Connecticut Filed Apr. 12, 1965, Ser. No. 447,463 9 Claims. (Cl. 200-50) This invention relates to an electrical power control unit having a safety switch assembly and, more particularly, to such a switch assembly including. a separable connector and plug which are selectively locked in the mated position by the switch actuating mechanism.

The manually operated electrical safety switch is widely used in industrial applications for control of supplying power to a load. Such a switch normally includes a metallic box, a cover, andan actuating handle extending from one side of the box. The handlecontrols a plurality of movable contacts which may be engaged or disengaged from fixed contacts connected to the power source. The movable contacts are connected by conductors to the external load. The switch normally includes arc shields and other devices for permitting the switch to be opened under rated load conditions without damage to the switch or hazard to the operator.

It is often desirable to employ separable wiring devices between the load and the safety switch. However, this practice creates safety problems in that the wiring device may be inadvertently disconnected while the switch is in the on position and supplying power to the load. This could result in dangerous arcing between the components of the wiring device. In order to overcome this problem, it has been proposed to provide an interlock between the switch and the wiring device such that the wiring device cannot be disconnected while the switch is closed. A prior art arrangement employs a female connector which is secured to the switch box and a special male plug of the interlocking type which is mated with the connector and then rotated to lock the components of the wiring device together in connected condition. The plug is provided with a radially extending lug and the switch includes a locking bar which projects into the path of the lug when the switch is closed to prevent the plug from being rotated and disconnected. The difiiculty with this arrangement is that it is only eifective when the special plug is employed and, therefore, a standard interlocking plug can be mated with, or removed from, the connector whether or not the switch is closed, thus destroyiing the safety function of the locking bar.

'. secured to the inner right side wall.

Accordingly, it is a primary object of the present invention to provide a safety switch-wiring device assembly in which the wiring device is inseparable when the safety switch is in its on position. Other objects are to provide such an assembly in which the switch cannot be closed unless the proper plug is inserted into the connector of the wiring device; in which the switch cannot be closed unless the plug is rotated to its locked position, and in which the switch is inoperable if a standard interlocking plug is inserted into the connector. The manner in which these objects are achieved will be more apparent from the following description, the appended claims, and the figures of the attached drawing, wherein:

FIG. 1 is a fragmentary front view of a safety switch and wiring device assembly with the front wall removed and an associated male plug in disconnected condition in accordance with this invention;

FIG. 2 is a cross sectional view taken substantially along line 22 of FIG. 1;

FIG. 3 is an enlarged detail view of the assembly of FIG. 2 showing the switch in its closed position;

FIG. 4 is a sectional view taken substantially along line 44 of FIG. 3, and

FIG. 5 is an end elevational view of the male plug when the switch is in its closed position.

With reference of FIGS. 1 and 2, there is illustrated a switch assembly including a switch box 10 of sheet metal having a generally U-shaped bracket 12 mounted on its inner right side wall. The bracket 12 has a forwardly extending portion 12' which supports the inner end of a shaft 14 which extends through the right side wall and is secured at its outer end to the actuating handle 16. Bracket portion 12 also includes a pair of spaced inwardly extending tabs forming an upper limit stop 12a and a lower limit stop 12b. Mounted between the bracket 12 and the right side wall of the box 10, and fixed to the shaft 14', is an actuating plate 18 which includes a pair of spaced, outwardly bent tabs forming a closing lug 18a and an opening lug 18b. A spring support bar 20 has one end .pivotally secured to the plate 18, and the other end extending through a slot in a guide bracket 22 which is The spring support bar 20 is narrowed and offset along its length to form a shoulder 20a and a compression coil spring 24 extends between the shoulder and the guide bracket 22.

A U-shaped actuating bar- 26 is pivotally mounted at one end to shaft 14 and is also provided at the left side of box 10(not shown). The right leg of the bar 26 extends outwardly, as shown, between the upper and lower limit stops 12a, 12b and the closing and opening lugs 18a and 18b. The actuating bar 26 carries an insulatingmember 28 which opens and closes the switch moving contacts 30.

As illustrated in FIGS. 1 and 2, the switch is in its open position with the handle 16 downward. To close the switch, the handle 16 -is raised. Plate 18 rotates with the handle, causing the opening lug 18b to lift off the actuati-n-g bar 26. As the plate continues to rotate in a counterclockwise direct-ion (as seen in FIG. 2) the closing lug 18a contacts the actuating bar 26. At the same time, the spring support bar 20 is being forced downwardly through the opening in the guide bracket 22 against the force of spring 24. As rotation continues, actuating bar 26 is moved upwardly by lug 18a and the pivot of spring support bar 20 passes dead center and toggles, causing release of the compressed spring 24 which assists in further movement of plate 18. The bar 26 and insulated member 28 close the switch contacts '30 and movement of the actuating 'bar 26 is limited by the upper limit stop 120: as shown in FIG. 3. The mechanism thus far described is conventional, but necessary to 'an understanding of certain features of the invention which are now to be described.

Mounted rigidly within an opening formed in the bottom of box 10 is the connector C of a separable interlocking wiring device, which also includes a mating male plug P. Interlocking wiring devices usable in this .invention are those of the type which lock together by rotating the plug relative to the connector. The illustrated wiring device is of the type generally disclosed more fully in United States Patent 2,102,625, which issued December 21, 1937. In this type of wiring device, the connector defines a socket, and the plug includes a post 32 which is insert-able into the socket and carries male contacts 34 on its outer surface. The contacts 34 not only eifect electrical connection, but also effect a mechanical lock when the plug is rotated relative to the connector after ther provided with a circumferentially extending mounting flange 40-by means of which the connector C is rigidly secured to the bottom wall of box 10 by screws 42. The electrical connection between connector C and the switch is made by means of conductors 44. It will be noted that the connector is positioned with that portion of shell 36 which defines guideway 38 nearest the right side wall of box 10.

' Plug P, which may be connected to a load by means of cable 46, is also provided with a metallic shell 48. Shell '48 is also substantially cylindrical with the exception of formed portion 48a which defines an internal keyway 50 having a cross section similar to that of guideway 38. Keyway 50 is so positioned that, when the plug and connector are mated and the plug rotated to its locking position, guideway 38 and keyway *50 are axially aligned with one another. The upper end of the keyway 50 is open and the lower end may optionally be either open or closed.

The bracket 12 within switch box 10'is provided with an arcuate slot 52 concentric with the shaft 14. A'sleeve 54 extends through this slot and is secured to plate 18 by means of a bolt 56 and nut 58. The sleeve 54' also passes through an opening in the upper end of a link bar 60 which is thereby pivotally mounted to andmovable with plate 18. The lower end of link bar 60 is pivotally secured to the upper end of lockin bar 62. The locking bar 62 extendsdownwardly into guideway 38 of the connector shell 36 with its lower end 62a normally disposed within the guideway 38 even when the switch is in the open position, as illustrated in FIGS. 1 and 2.

In explaining the operation of this invention, it will first be assumed that the switch is in the open position, as illustrated in FIGS. 1 and 2. Post 32 of plug P is inserted into the socket of connector C and, when these parts are fully mated, the plug P is rotated clockwise, causing the contacts 34 to lock within the connector C in electrical contact with the connector contacts. At the same time, the'shell 48 of the plug rotates untilthe keyway- 50 becomes aligned with the guideway 38 of the connector shell. The switch may as; be closed by forcing handle 16 upwardly. As the 'pl :13 rotates in a counterclockwise direction (as seen in FIG. 2) to close the moving contacts 30, the sleeve 54 is caused to move downwardly in the arcuate slot 52. This forces the link bar 60 and the locking bar '62 downwardly, causing the locking bar 62 to slide in the guideway 38 and advance into the keyway 50 of the plug P, this advancement continuing until the switch is in the fully closed position and the mechanism is in the condition illustrated in FIG. 3. In this condition, the components of the wiring device are completely interlocked and the plug P cannot be withdrawn as long as the switch is in the closed posit-ion, because of the confinement ofthe lower end of the look ing bar 62a in the keyway 50.

FIGS. 4 and illustrate very important features of this invention. It will be noted from these illustrations that the locking bar 62 lies across the region-that would normally be covered by the continuation of the cylindrical portion of shell 48 if no keyway were provided. The significance of this feature is that it prevents insertion of the plug P into the connector C if the switch is closed, and it prevents usage of conventional plugs with the connector C. When the switch is closed, the lower end 62a projects out of guideway 38 in position to contact the end of any plug shell and prevent insertion movement of the plug. If the switch were open a plug without the formed portion 48a could be inserted into the connector C and rotated, but it would not be possible to close the switch because on attempted closure of the switch the lower end 62a of the locking bar 62 would contact the end of the shell and prevent full closure of the switch. This is a very important feature and a result which is not achieved by prior art devices which utilize radially extending lugs on the plug to prevent rotation of the plug when the switch is closed, for the prior art devices will accept conventional plugs and permit their rotation even if the switch is closed, an undesirable operation the inventive device will not permit. It will, therefore, be noted that in addition to preventing removal of the inventive plug P when the switch is closed, neither the inventive plug P, the special prior art plug with a radial lug nor a conventional plug can be inserted into the connector of the invention when the switchis closed. If a conventional or prior art plug is inserted into the connector when the switch is open, the switch cannot thereafter be closed. These are important safety features not present in prior art devices.

It is believed that those skilled in the art will appreciate the many features and advantages of this invention, and it will also be apparent to them that many modifications may be made in the invention without departing from its spirit and scope. For example, by a slight modification of the linkage, it is possible to design the invention so that the plug could not be removed even when the switch is in the toff position. This would prevent unauthorized removal during shutdown of the supplied unit. Accordingly, the foregoing description is to be construed as illustrative only, rather than limiting. The invention is limited only by the scope of the following claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical power supply control unit which comprises: a housing; two position switch means in said housing; actuating handle means mounted on said housing; switch operating means intermediate said handle means and said switch means; a connector mounted on said housing and electrically connected to said switch means; separable plug means arranged to be rotatably interlocked with said connector, said plug means defining a keyway therein; and locking means operable from said switch operating means and disposed to extend into said keyway when said switch means is in one of its positions to prevent rotation of said plug means relative to said connector.

2. The unit of claim 1 wherein said connector defines a guideway aligned with said keyway when said plug means is interlocked with said connector.

3. The unit of claim 1 wherein said switch operating means comprises plate means operable from said handle means and wherein said locking means comprises a linking bar having a first end pivotally secured to said plate means, and a locking bar having one end pivotally secured to the second end of said linking bar and the other end extendable into said keyway.

4. An electrical power supply control unit which comprises: a housing; switch means in said housing; actuating handle means mounted on said housing; actuating plate means mounted within said housing for rotation by said handle means to open and close said switch means; a connector mounted on said housing and electrically connected to said switch means; separable plug means arranged to be rotatably interlocked with said connector, said plug means defining a keyway therein; a linking bar having a first end pivotally secured to said actuating plate means and a second end; and a locking bar having a first end pivotally secured to the second end of said linking bar and a second end insertable into said keyway when said switch means is in its closed position and said connector and plug means are interlocked.

5. The unit of claim 4 wherein said connector defines a guideway reciprocatingly enclosing said locking bar therein.

6. The unit of claim 4 wherein said plug means includes a substantially cylindrical metal shell, a formed portion thereof defining said keyway, the cross section of said keyway at the mating end of said plug means lying on the circumference of the cylindrical portion of said shell.

7. The unit of claim 5 wherein said connector includes a substantially cylindrical metal shell and a formed portion thereof defining said guideway;

8. An electrical plug which comprises: a body member of insulating material; a plurality of male contact means on said body member; and a substantially cylindrical metal shell enclosing said body member and including a formed portion defining a keyway therein extending parallel to the longitudinal axis of said cylinder, the cross section of said keyway at the mating end of said plug lying on the circumference of the cylindrical portion of said shell.

9. An electrical power supply control unit which comprises: a housing; switch means in said housing; actuating handle means mounted on said housing; actuating plate means mounted within said housing for rotation by said handle means to open and close said switch means; a connector mounted on said housing and including a metallic shell defining a guideway through said housing; a linking bar having a first end pivotally secured to said actuating plate means and a second end; and a locking bar having a first end pivotally secured to the second end of said linking bar and a second end reciprocatingly enclosed within said guideway.

References Cited by the Examiner UNITED STATES PATENTS 1,161,582 11/1915 Anklam 200-51 ROBERT K. SCI-IAEFER, Primary Examiner.

J. SCOTT, Assistant Examiner. 

1. AN ELECTRICAL POWER SUPPLY CONTROL UNIT WHICH COMPRISES: A HOUSING; TWO POSITION SWITCH MEANS IN SAID HOUSING; ACTUATING HANDLE MEANS MOUNTED ON SAID HOUSING; SWITCH OPERATING MEANS INTERMEDIATE SAID HANDLE MEANS AND SAID SWITCH MEANS; A CONNECTOR MOUNTED ON SAID HOUSING A ELECTRICALLY CONNECTED TO SAID SWITCH MEANS; SEPARABLE PLUG MEANS ARRANED TO BE ROTATABLY INTERLOCKED WITH SAID CONNECTOR, SAID PLUG MEANS DEFINING A KEYWAY THEREIN; AND LOCKING MEANS OPERABLE FROM SAID SWITCH OPERAT- 